U.S. patent number 10,077,502 [Application Number 14/778,159] was granted by the patent office on 2018-09-18 for silver-plated product.
This patent grant is currently assigned to Dowa Metaltech Co., Ltd.. The grantee listed for this patent is DOWA METALTECH CO., LTD.. Invention is credited to Hiroshi Miyazawa, Masafumi Ogata, Keisuke Shinohara, Akira Sugawara.
United States Patent |
10,077,502 |
Shinohara , et al. |
September 18, 2018 |
Silver-plated product
Abstract
There is provided a silver-plated product which has good thermal
resistance, bendability and wear resistance. In a silver-plated
product wherein a surface layer of silver having a thickness of 10
.mu.m or less is formed on a base material of copper or a copper
alloy, the full-width at half maximum of a rocking curve on a
preferred orientation plane (preferably {200} or {111} plane) of
the surface layer is caused to be 2 to 8.degree., preferably 3 to
7.degree., to improve the out-of-plane orientation of the surface
layer to improve the thermal resistance, bendability and wear
resistance of the silver-plated product.
Inventors: |
Shinohara; Keisuke (Saitama,
JP), Ogata; Masafumi (Saitama, JP),
Miyazawa; Hiroshi (Saitama, JP), Sugawara; Akira
(Shizuoka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
DOWA METALTECH CO., LTD. |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Dowa Metaltech Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
51579892 |
Appl.
No.: |
14/778,159 |
Filed: |
February 18, 2014 |
PCT
Filed: |
February 18, 2014 |
PCT No.: |
PCT/JP2014/054252 |
371(c)(1),(2),(4) Date: |
September 18, 2015 |
PCT
Pub. No.: |
WO2014/148200 |
PCT
Pub. Date: |
September 25, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
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US 20160281253 A1 |
Sep 29, 2016 |
|
Foreign Application Priority Data
|
|
|
|
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Mar 21, 2013 [JP] |
|
|
2013-057510 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D
7/00 (20130101); H01H 1/025 (20130101); H01H
11/041 (20130101); C25D 3/46 (20130101); C25D
5/10 (20130101); H01H 2011/046 (20130101); C25D
5/34 (20130101); H01R 13/03 (20130101) |
Current International
Class: |
B32B
15/01 (20060101); H01H 11/04 (20060101); H01H
1/025 (20060101); C25D 7/00 (20060101); C25D
5/10 (20060101); C25D 3/46 (20060101); C25D
5/34 (20060101); H01R 13/03 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
2 749 673 |
|
Jul 2014 |
|
EP |
|
3889718 |
|
Dec 2006 |
|
JP |
|
4279285 |
|
Mar 2009 |
|
JP |
|
2010-146925 |
|
Jul 2010 |
|
JP |
|
2012-162775 |
|
Aug 2012 |
|
JP |
|
2012162775 |
|
Aug 2012 |
|
JP |
|
2013/047628 |
|
Apr 2013 |
|
WO |
|
Other References
International Search Report for PCT/JP2014/054252 dated May 12,
2014. cited by applicant .
European search report for application No. 14 76 8027 dated Oct.
20, 2016. cited by applicant.
|
Primary Examiner: Schleis; Daniel J
Attorney, Agent or Firm: Bachman & LaPointe, PC
Claims
The invention claimed is:
1. A silver-plated product comprising: a base material of copper or
a copper alloy; and a surface layer of silver which is formed on
the base material, wherein the full-width at half maximum of a
rocking curve on a preferred orientation plane of the surface layer
is 6 to 8.degree., and the preferred orientation plane of the
surface layer is {200} plane.
2. A silver-plated product as set forth in claim 1, wherein said
full-width at half maximum of the rocking curve on the preferred
orientation plane of the surface layer is 6 to 7.degree..
3. A silver-plated product as set forth in claim 1, wherein said
surface layer has a thickness of 10 .mu.m or less.
4. A contact or terminal part which is made of a silver-plated
product as set forth in any one of claims 1, 2 and 3.
Description
TECHNICAL FIELD
The present invention generally relates to a silver-plated product.
More specifically, the invention relates to a silver-plated product
used as the material of contact and terminal parts, such as
connectors, switches and relays, which are used for automotive
and/or household electric wiring.
BACKGROUND ART
As conventional materials of contact and terminal parts, such as
connectors and switches, there are used plated products wherein a
base material of stainless steel, copper, a copper alloy or the
like, which is relatively inexpensive and which has excellent
corrosion resistance, mechanical characteristics and so forth, is
plated with tin, silver, gold or the like in accordance with
required characteristics, such as electrical and soldering
characteristics.
Tin-plated products obtained by plating a base material of
stainless steel, copper, a copper alloy or the like, with tin are
inexpensive, but they do not have good corrosion resistance.
Gold-plated products obtained by plating such a base material with
gold have excellent corrosion resistance and high reliability, but
the costs thereof are high. On the other hand, silver-plated
products obtained by plating such a base material with silver are
inexpensive in comparison with gold-plated products and have
excellent corrosion resistance in comparison with tin-plated
products.
As such a silver-plated product, there is proposed a metal plate
for electrical contacts, wherein a silver plating film having a
thickness of 1 .mu.m is formed on a copper plating film having a
thickness of 0.1 to 0.5 .mu.m which is formed on a nickel plating
film having a thickness of 0.1 to 0.3 .mu.m which is formed on the
surface of a thin base material plate of stainless steel (see,
e.g., Japanese Patent No. 3889718). There is also proposed a
silver-coated stainless bar for movable contacts, wherein a surface
layer of silver or a silver alloy having a thickness of 0.5 to 2.0
.mu.m is formed on an intermediate layer of at least one of nickel,
a nickel alloy, copper and a copper alloy having a thickness of
0.05 to 0.2 .mu.m, the intermediate layer being formed on an
activated underlying layer of nickel which has a thickness of 0.01
to 0.1 .mu.m and which is formed on the surface of a base material
of stainless steel (see, e.g., Japanese Patent No. 4279285).
Moreover, there is proposed a silver-coated material for movable
contact parts, wherein a surface layer of silver or a silver alloy
having a thickness of 0.2 to 1.5 .mu.m is formed on an intermediate
layer of copper or a copper alloy having a thickness of 0.01 to 0.2
.mu.m, the intermediate layer being formed on an underlying layer
of any one of nickel, a nickel alloy, cobalt or a cobalt alloy
which has a thickness of 0.005 to 0.1 .mu.m and which is formed on
a metallic substrate of copper, a copper alloy, iron or an iron
alloy, and wherein the arithmetic average roughness Ra of the
metallic substrate is 0.001 to 0.2 .mu.m, and the arithmetic
average roughness Ra after forming the intermediate layer is 0.001
to 0.1 .mu.m (see, e.g., Japanese patent Laid-Open No.
2010-146925).
However, if a silver plating film is formed on the surface of a
base material of copper or a copper alloy or on the surface of an
underlying layer of copper or a copper alloy formed on a base
material in such a conventional silver-plated product, there is a
problem in that copper diffuses to form CuO on the surface of the
silver plating film to raise the contact resistance thereof if it
is used in a high-temperature environment. There is also a problem
in that cracks are formed in the silver-plated product to expose
the base material if the silver-plated product is worked in a
complicated shape or in a shape of small contact and terminal
parts, such as connectors and switches. Moreover, there is a
problem in that the silver plating film is easily worn.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to eliminate the
above-described conventional problems and to provide a
silver-plated product having good thermal resistance, bendability
and wear resistance.
In order to accomplish the aforementioned object, the inventors
have diligently studied and found that it is possible to produce a
silver-plated product having good thermal resistance, bendability
and wear resistance if the full-width at half maximum of a rocking
curve on a preferred orientation plane of a surface layer is 2 to
8.degree. in a silver-plated material wherein the surface layer of
silver is formed on a base material. Thus, the inventors have made
the present invention.
According to the present invention, a silver-plated product
comprises: a base material; and a surface layer of silver which is
formed on the base material, wherein the full-width at half maximum
of a rocking curve on a preferred orientation plane of the surface
layer is 2 to 8.degree.. In this silver-plated product, the
full-width at half maximum of the rocking curve on the preferred
orientation plane of the surface layer is preferably 3 to
7.degree., and the preferred orientation plane of the surface layer
is preferably {200} or {111} plane. The base material is preferably
made of copper or a copper alloy, and the surface layer preferably
has a thickness of 10 .mu.m or less.
According to the present invention, there is provided a contact or
terminal part which is made of the above-described silver-plated
product.
According to the present invention, it is possible to produce a
silver-plated product having good thermal resistance, bendability
and wear resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing a rocking curve on a preferred
orientation plane of a silver plating film of a silver-plated
product in each of Example 3 and Comparative Example 3, and a
full-width at half maximum thereof.
BEST MODE FOR CARRYING OUT THE INVENTION
In the preferred embodiment of a silver-plated product according to
the present invention, the full-width at half maximum of a rocking
curve on a preferred orientation plane of a surface layer of a
silver-plated product, wherein the surface layer of silver is
formed on a base material, is 2 to 8.degree., preferably 3 to
7.degree..
If the full-width at half maximum of the rocking curve on the
preferred orientation plane of the surface layer of silver is thus
2 to 8.degree. preferably 3 to 7.degree., the out-of-plane
orientation of the surface layer is improved, so that it is
possible to improve the thermal resistance, bendability and wear
resistance of the silver-plated product.
In this silver-plated product, the preferred orientation plane of
the surface layer is preferably {200} or {111} plane. The base
material is preferably made of copper or a copper alloy, and the
surface layer preferably has a thickness of 10 .mu.m or less.
The surface layer of silver of the silver-plated product can be
formed by electroplating at a current density of 3 to 10 A/dm.sup.2
and a liquid temperature of 10 to 40.degree. C. (preferably 15 to
30.degree. C.) in a silver plating solution which comprises silver
potassium cyanide (KAg(CN).sub.2), potassium cyanide (KCN), and 3
to 30 mg/L of potassium selenocyanate (KSeCN) and wherein the
concentration of selenium in the silver plating solution is 5 to 15
mg/L, the mass ratio of silver to free cyanogen being in the range
of from 0.9 to 1.8.
Examples of a silver-plated product according to the present
invention will be described below in detail.
Example 1
First, a pure copper plate having a size of 67 mm.times.50
mm.times.0.3 mm was prepared as a base material (a material to be
plated). The material to be plated and a SUS plate were put in an
alkali degreasing solution to be used as a cathode and an anode,
respectively, to carry out electrolytic degreasing at 5 V for 30
seconds. The material thus electrolytic-degreased was washed, and
then, pickled for 15 seconds in a 3% sulfuric acid.
Then, the material to be plated and a titanium electrode plate
coated with platinum were used as a cathode and an anode,
respectively, to electroplate (silver-strike-plate) the material at
a current density of 2.5 A/dm.sup.2 for 10 seconds in a silver
strike plating bath comprising 3 g/L of silver potassium cyanide
and 90 g/L of potassium cyanide while stirring the solution at 400
rpm by a stirrer.
Then, the material to be plated and a silver electrode plate were
used as a cathode and an anode, respectively, to electroplate
(silver-plate) the material at a current density of 5 A/dm.sup.2
and a liquid temperature of 18.degree. C. in a silver plating bath
comprising 148 g/L of silver potassium cyanide (KAg(CN).sub.2), 140
g/L of potassium cyanide and 18 mg/L of potassium selenocyanate
(KSeCN) while stirring the solution at 400 rpm by a stirrer, until
a silver plating film having a thickness of 3 micrometers was
formed. Furthermore, in the used silver plating bath, the
concentration of Se was 10 mg/L, and the concentration of Ag was 80
g/L, the concentration of free CN being 56 g/L, and the mass ratio
of Ag to free CN being 1.44.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
a silver plating film were evaluated.
In order to evaluate the crystal orientation of the silver plating
film of the silver-plated product, an X-ray diffractometer (XRD)
(Full-Automatic Multi-Purpose Horizontal X-ray diffractometer,
Smart Lab produced by RIGAKU Corporation) was used for obtaining an
X-ray diffraction pattern by carrying out the 2.theta./.theta. scan
using an X-ray tube of Cu and the K.beta. filter method. Then, from
the X-ray diffraction pattern thus obtained, each of X-ray
diffraction peak intensities (intensities of X-ray diffraction
peaks) on {111}, {200}, {220} and {311} planes of the silver
plating film was corrected by relative intensity ratios (relative
intensity ratios in the measurement of powder) described on JCPD
card No. 40783. Then, the plane orientation of an X-ray diffraction
peak, at which each of values (corrected intensities) obtained by
the above-described correction was highest, was evaluated as the
direction of the crystal orientation (the preferred orientation
plane) of the silver plating film to obtain a diffraction angle
2.theta. of the X-ray diffraction peak on the preferred orientation
plane in the scanning range of 2.theta./.theta. to obtain a rocking
curve (intensity curve) by scanning an angle .omega. of incidence
at a fixed diffraction angle 2.theta. to obtain a full-width at
half maximum of the rocking curve. Furthermore, it is possible to
determine the strength of the out-of-plane orientation by the
full-width at half maximum of the rocking curve, and the
out-of-plane orientation is stronger as the full-width at half
maximum of the rocking curve is sharper (i.e., the full-width at
half maximum is smaller). As a result, in the silver-plated product
in this example, the crystals of the silver plating film were
orientated to {200} plane (orientated so that {200} plane was
directed to the surface (plate surface) of the silver-plated
product), i.e., the preferred orientation plane of the silver
plating film was {200} plane. The full-width at half maximum of the
rocking curve was a small value of 3.8.degree., so that the
out-of-plane orientation was strong.
The thermal resistance of the silver-plated product was evaluated
by measuring a contact resistance thereof at a load of 50 gf by
means of an electrical contact simulator (CRS-1 produced by
Yamasaki-Seiki Co., Ltd.) before and after a heat-proof test in
which the silver-plated product was heated at 200.degree. C. for
144 hours by means of a dryer (OF450 produced by AS ONE
Corporation). As a result, the contact resistance of the
silver-plated product was 0.9 m.OMEGA. before the heat-proof test
and 2.4 m.OMEGA. after the heat-proof test. Thus, the contact
resistance after the heat-proof test was a good value which was not
higher than 5 m.OMEGA., so that the rise of the contact resistance
was restrained after the heat-proof test.
The bendability of the silver-plated product was evaluated on the
basis of the presence of cracks in a bent portion of the
silver-plated product by observing the bent portion at a power of
1000 by means of a microscope (Digital Microscope VHX-1000 produced
by KEYENCE CORPORATION) after the silver-plated product was bent by
90 degrees at R=0.1 in a direction perpendicular to the direction
of rolling of the base material in accordance with the V-block
method described in Japanese Industrial Standard (JIS) Z2248. As a
result, cracks were not observed, so that the bendability of the
silver-plated product was good.
The wear resistance of the silver plating film of the silver-plated
product was evaluated as follows. First, about 30 mg of a grease
(MULTEMP D No. 2 produced by Kyodo Yushi Co., Ltd.) per an area of
8 cm.sup.2 was applied on the plate surface of the silver-plated
product to be uniformly extended. Then, a sliding tester was used
for causing a silver rivet containing 89.7 wt % of Ag and 0.3 wt %
of Mg and having a curvature radius of 8 mm to slide as a
reciprocation sliding motion on the plate surface of the
silver-plated product, to which a current of 500 mA was applied,
while the silver rivet was pressed against to the plate surface
thereof at a load of 100 gf. After such a reciprocation sliding
motion (sliding distance of 5 mm, sliding speed of 12 mm/sec) was
continued 300,000 times, the abrasion loss of the silver plating
film was measured for evaluating the wear resistance. As a result,
the abrasion loss of the silver plating film was 0.6 .mu.m, so that
the wear resistance of the silver-plated product was good.
Example 2
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) in a silver plating bath comprising 148 g/L of
silver potassium cyanide, 140 g/L of potassium cyanide and 11 mg/L
of potassium selenocyanate. Furthermore, in the used silver plating
bath, the concentration of Se was 6 mg/L, and the concentration of
Ag was 80 g/L, the concentration of free CN being 56 g/L, and the
mass ratio of Ag to free CN being 1.44.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {200} plane, i.e., the preferred orientation plane of
the silver plating film was {200} plane. The full-width at half
maximum of the rocking curve was a small value of 5.2.degree., so
that the out-of-plane orientation was strong. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 1.0 m.OMEGA. before the
heat-proof test and 2.4 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was a good value
which was not higher than 5 m.OMEGA., so that the rise of the
contact resistance was restrained after the heat-proof test. In the
evaluation of the bendability of the silver-plated product, cracks
were not observed, so that the bendability of the silver-plated
product was good. In the evaluation of the wear resistance of the
silver-plated product, the abrasion loss of the silver plating film
was 0.6 .mu.m, so that the wear resistance of the silver-plated
product was good.
Example 3
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) in a silver plating bath comprising 148 g/L of
silver potassium cyanide, 140 g/L of potassium cyanide and 6 mg/L
of potassium selenocyanate. Furthermore, in the used silver plating
bath, the concentration of Se was 3 mg/L, and the concentration of
Ag was 80 g/L, the concentration of free CN being 56 g/L, and the
mass ratio of Ag to free CN being 1.44.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {200} plane, i.e., the preferred orientation plane of
the silver plating film was {200} plane. The full-width at half
maximum of the rocking curve was a small value of 6.0.degree., so
that the out-of-plane orientation was strong. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 1.0 m.OMEGA. before the
heat-proof test and 1.9 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was a good value
which was not higher than 5 m.OMEGA., so that the rise of the
contact resistance was restrained after the heat-proof test. In the
evaluation of the bendability of the silver-plated product, cracks
were not observed, so that the bendability of the silver-plated
product was good. In the evaluation of the wear resistance of the
silver-plated product, the abrasion loss of the silver plating film
was 0.4 .mu.m, so that the wear resistance of the silver-plated
product was good.
Example 4
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) at a liquid temperature of 25.degree. C. in a
silver plating bath comprising 111 g/L of silver potassium cyanide,
120 g/L of potassium cyanide and 18 mg/L of potassium
selenocyanate. Furthermore, in the used silver plating bath, the
concentration of Se was 10 mg/L, and the concentration of Ag was 60
g/L, the concentration of free CN being 48 g/L, and the mass ratio
of Ag to free CN being 1.26.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {111} plane, i.e., the preferred orientation plane of
the silver plating film was {111} plane. The full-width at half
maximum of the rocking curve was a small value of 6.3.degree., so
that the out-of-plane orientation was strong. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 0.8 m.OMEGA. before the
heat-proof test and 1.7 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was a good value
which was not higher than 5 m.OMEGA., so that the rise of the
contact resistance was restrained after the heat-proof test. In the
evaluation of the bendability of the silver-plated product, cracks
were not observed, so that the bendability of the silver-plated
product was good. In the evaluation of the wear resistance of the
silver-plated product, the abrasion loss of the silver plating film
was 0.4 .mu.m, so that the wear resistance of the silver-plated
product was good.
Comparative Example 1
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) in a silver plating bath comprising 148 g/L of
silver potassium cyanide, 140 g/L of potassium cyanide and 73 mg/L
of potassium selenocyanate. Furthermore, in the used silver plating
bath, the concentration of Se was 40 mg/L, and the concentration of
Ag was 80 g/L, the concentration of free CN being 56 g/L, and the
mass ratio of Ag to free CN being 1.44.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {111} plane, i.e., the preferred orientation plane of
the silver plating film was {111} plane. The full-width at half
maximum of the rocking curve was a large value of 13.3.degree., so
that the out-of-plane orientation was weak. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 0.7 m.OMEGA. before the
heat-proof test and 574.5 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was very high, so
that the rise of the contact resistance was not restrained after
the heat-proof test. In the evaluation of the bendability of the
silver-plated product, cracks were observed, so that the
bendability of the silver-plated product was not good. In the
evaluation of the wear resistance of the silver-plated product, the
abrasion loss of the silver plating film was 1.5 .mu.m, so that the
wear resistance of the silver-plated product was not good.
Comparative Example 2
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) in a silver plating bath comprising 148 g/L of
silver potassium cyanide, 140 g/L of potassium cyanide and 2 mg/L
of potassium selenocyanate. Furthermore, in the used silver plating
bath, the concentration of Se was 1 mg/L, and the concentration of
Ag was 80 g/L, the concentration of free CN being 56 g/L, and the
mass ratio of Ag to free CN being 1.44.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {111} plane, i.e., the preferred orientation plane of
the silver plating film was {111} plane. The full-width at half
maximum of the rocking curve was a large value of 8.1.degree., so
that the out-of-plane orientation was weak. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 1.0 m.OMEGA. before the
heat-proof test and 6.5 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was higher than 5
m.OMEGA., so that the rise of the contact resistance was not
restrained after the heat-proof test. In the evaluation of the
bendability of the silver-plated product, cracks were observed, so
that the bendability of the silver-plated product was not good. In
the evaluation of the wear resistance of the silver-plated product,
the abrasion loss of the silver plating film was 1.5 .mu.m, so that
the wear resistance of the silver-plated product was not good.
Comparative Example 3
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) at a current density of 1.2 A/dm.sup.2 and a liquid
temperature of 47.degree. C. in a silver plating bath comprising
150 g/L of silver potassium cyanide and 90 g/L of potassium
cyanide. Furthermore, in the used silver plating bath, the
concentration of Se was 0 mg/L, and the concentration of Ag was 81
g/L, the concentration of free CN being 36 g/L, and the mass ratio
of Ag to free CN being 2.25.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {111} plane, i.e., the preferred orientation plane of
the silver plating film was {111} plane. The full-width at half
maximum of the rocking curve was a large value of 10.8.degree., so
that the out-of-plane orientation was weak. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 0.9 m.OMEGA. before the
heat-proof test and 2.0 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was a good value
which was not higher than 5 m.OMEGA., so that the rise of the
contact resistance was restrained after the heat-proof test. In the
evaluation of the bendability of the silver-plated product, cracks
were observed, so that the bendability of the silver-plated product
was not good. In the evaluation of the wear resistance of the
silver-plated product, the abrasion loss of the silver plating film
was 2.0 .mu.m, so that the wear resistance of the silver-plated
product was not good.
Comparative Example 4
A silver-plated product was produced by the same method as that in
Example 1, except that the material to be plated was electroplated
(silver-plated) at a current density of 2 A/dm.sup.2 and a liquid
temperature of 25.degree. C. in a silver plating bath comprising
111 g/L of silver potassium cyanide, 120 g/L of potassium cyanide
and 18 mg/L of potassium selenocyanate. Furthermore, in the used
silver plating bath, the concentration of Se was 10 mg/L, and the
concentration of Ag was 60 g/L, the concentration of free CN being
48 g/L, and the mass ratio of Ag to free CN being 1.26.
With respect to a silver-plated product thus produced, the crystal
orientation, thermal resistance, bendability and wear resistance of
the silver plating film were evaluated by the same methods in those
in Example 1.
As a result, in the evaluation of the crystal orientation of the
silver plating film, the crystals of the silver plating film were
orientated to {220} plane, i.e., the preferred orientation plane of
the silver plating film was {220} plane. The full-width at half
maximum of the rocking curve was a large value of 13.0.degree., so
that the out-of-plane orientation was weak. In the evaluation of
the thermal resistance of the silver-plated product, the contact
resistance of the silver-plated product was 1.0 m.OMEGA. before the
heat-proof test and 11.1 m.OMEGA. after the heat-proof test. Thus,
the contact resistance after the heat-proof test was higher than 5
m.OMEGA., so that the rise of the contact resistance was not
restrained after the heat-proof test. In the evaluation of the
bendability of the silver-plated product, cracks were observed, so
that the bendability of the silver-plated product was not good. In
the evaluation of the wear resistance of the silver-plated product,
the abrasion loss of the silver plating film was 1.9 .mu.m, so that
the wear resistance of the silver-plated product was not good.
The producing conditions and characteristics of the silver-plated
product in each of these examples and comparative examples are
shown in Tables 1 and 2, respectively. In order to explain the
rocking curve and the full-width at half maximum thereof, FIG. 1
shows the rocking curve on the preferred orientation plane of the
silver plating film of the silver-plated product in each of Example
3 and Comparative Example 3 and the full-width at half maximum
thereof.
TABLE-US-00001 TABLE 1 Silver Plating Composition of Silver
Conditions Plating Bath Current Plating K[Ag(CN).sub.2] KCN KSeCN
Density Temp. (g/L) (g/L) (mg/L) (A/dm.sup.2) (.degree. C.) Example
1 148 140 18 5 18 Example 2 148 140 11 5 18 Example 3 148 140 6 5
18 Example 4 111 120 18 5 25 Comp. 1 148 140 73 5 18 Comp. 2 148
140 2 5 18 Comp. 3 150 90 0 1.2 47 Comp. 4 111 120 18 2 25
TABLE-US-00002 TABLE 2 Full-Width at Half Maximum of Contact
Contact Rocking Resistance Resistance Curve before after on
Preferred Heat Heat Bendability Abrasion Preferred Orientation
Proof Proof (Presence Loss Orientation Plane Test Test of of Ag
Plane (deg) (m.OMEGA.) (m.OMEGA.) Cracks) (.mu.m) Ex. 1 {200} 3.8
0.9 2.4 None 0.6 Ex. 2 {200} 5.2 1.0 2.4 None 0.6 Ex. 3 {200} 6.0
1.0 1.9 None 0.4 Ex. 4 {111} 6.3 0.8 1.7 None 0.4 Comp. 1 {111}
13.3 0.7 574.5 Presence 1.5 Comp. 2 {111} 8.1 1.0 6.5 Presence 1.0
Comp. 3 {111} 10.8 0.9 2.0 Presence 2.0 Comp. 4 {220} 13.0 1.0 11.1
Presence 1.9
As can be seen from Tables 1 and 2, the silver-plated product in
each of Examples 1 through 4, wherein the full-width at half
maximum of the rocking curve on the preferred orientation plane of
the silver plating film was 3 to 7.degree., has good thermal
resistance, bendability and wear resistance.
* * * * *